Solid block, powdered, pellet, liquid and other chemical concentrate materials can be combined with water to form a liquid concentrate solution. Such a liquid concentrate solution is pumped to a use locus such as a warewashing machine, a laundry machine, a janitorial bucket or closet sink, a clean-in-place system, as a lubricant in a conveyor and a variety of other locations where cleaners, sanitizers, rinse aids, lubricants and other liquid functional materials find utility. In such systems, the liquid concentrate is typically aqueous material is often pumped from a container or a reservoir, diluted if necessary and delivered to the use locus. The liquid in the container or reservoir is often a liquid concentrate and is purchased from a supplier, but can also be a liquid concentrate made from solid, powdered or pelletized material. Regardless of the source of the liquid concentrate, the liquid can be depleted from its container or reservoir during use. In order to obtain consistent results from the liquid concentrate, the empty container or empty reservoir condition must be made known to the staff personnel immediately for replacement with fresh liquid or a full container of liquid. Should the system no longer provide adequate concentrate to the use locus, the functionality of the material can be reduced, or lost altogether, resulting in a failure to clean, a failure to reduce microbial populations adequately, a failure to rinse, a failure to lubricate or other failure of machine or process. The presence of an insubstantial or no liquid material can result in simply a temporary reduction of function or capacity. A complete absence of function or capacity can in certain rare circumstances result in machine damage.
A large variety of proof of flow or empty product detector mechanisms have been developed. Many such systems are complicated in construction, slow in response, or offer intermittent results. A number of low product or product empty alarm systems use floats that can be used as the empty product detectors. One such patent, Schneier, Canadian Patent No. 1,012,630, claims a low product alarm comprising a float in a hollow float chamber, a product inlet to the chamber and a product outlet from the chamber. The inlets and outlets are formed in the chamber base. The chamber includes a float and sensor switch. The chamber also comprises a second valved outlet installed in the top of the device that is used as a priming line. In use, the sensing device is filled with liquid by drawing fluid using a pump through the low product alarm, then through the valved priming line, until full. At that point, the valved priming line is closed using a valve installed in the line and operations are continued by drawing liquid from the inlet tube into the product alarm, then to the outlet, then to the pump and to the use locus. When the source of liquid is depleted, the float chamber is emptied, the float drops, triggering a product empty signal. While the Schneier device provides some degree of successful product sensing, its design is complex with multiple inlets and outlets and valved primer lines.
A substantial needs exists for a simple improved low product sensor that can provide a low product alarm with minimal complexity and maximum reliability and sensitivity.